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A slab of synthetic diamond 4×4×1.5 mm3 has been studied in Bragg-case, simultaneously in reflected and transmitted beams, using a double-crystal topographic method with a synchrotron source of x-rays. The examined diamond had been grown by the reconstitution method and was of a cuboctahedral habit with two large artificially cut surfaces parallel to (001) planes. A very sensitive double-crystal arrangement was used with the 008 diamond reflexion matching the 1151 silicon reflexion selecting 0.802 Å radiation. Both reflected Kvector g and transmitted Kvector 0 beam topographs revealed the images of dislocations and many details of the growth sector structure. The pairs of topographs thus obtained were not entirely complementary. Apart from the different foreshortening, the transmitted beam topographs were less sensitive and reproduced more distinctly defects closer to the exit surface. The results are compared with those obtained using other methods, especially the single-crystal section and projection topography. The images of dislocations in Kvector g and Kvector 0 topographs were compared with theoretical images obtained by numerical integration of the Takagi-Taupin equations, including modeling of impurity segregation in growth bands and taking into account the angular divergence of the monochromatized beam. The applied method provided a reasonable correspondence between the simulated and experimental images and confirmed that the images of dislocation outcrops on the entrance surface dominate both the Kvector g and Kvector 0 topographs. [ABSTRACT FROM AUTHOR]

Calcium molybdate CaMoO4 crystals are perspective materials for many applications in acoustic-electronics, acoustic-optics and nonlinear optics. They are also used as laser hosts, scintillators, different kinds of substrates and active elements of ionizing radiation detectors. For all these applications large-sized single crystals of high structural quality are required. The samples of CaMoO4 crystals have been investigated by means of synchrotron white beam topography, monochromatic beam topography and conventional X-ray Lang projection topography. The high-resolution rocking curves have also been taken using synchrotron and conventional arrangements. The topographs showed a rather good crystallographic perfection of the crystals. In particular, they did not reveal any segregation fringes proving high homogeneity of the chemical composition. Relatively high densities (<104 cm−2) of weak point-like diffraction contrasts were observed, which can be most probably interpreted as dislocation outcrops. The distinct main imperfection of the investigated crystals was variously developed block structure. The evaluation of lattice misorientation was realized by means of projection and section white beam synchrotron radiation topographs. The evaluated misorientation between various blocks was in the range of several arc minutes. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The defect structure investigations of selected ferroelectric niobates such as SrxBa1-xNb2O6 (SBN), CaxBa1-xNb2O6 (CBN) and mixed (Ca0.28Ba0.72)y(Sr0.61Ba0.39)1-yNb2O6 (CSBN) single crystals grown by the Czochralski method have been performed by means of synchrotron and conventional diffraction topography and scanning electron microscopy. A new characteristic phenomenon has been indicated in CSBN crystals, which consisted in occurrence of two different systems of segregation fringes forming a crossing pattern. The first of them is the normal one, connected with the subsequent positions of the growth surface and coaxial with the core and the boundaries of the crystal. The second one, crossing the previous, is related to a kind of 'ghost' pattern reproducing some chemical composition changes in the new growing part of the crystal. Some rod-like inclusions were also revealed around the core in the central part of samples cut out from various crystals. The scanning electron microscopic studies of selectively chemical etched samples revealed a domain structure in the SrxBa1-xNb2O6, CaxBa1-xNb2O6 and CSBN crystals. The ferroelectric domains were located along [001] direction. The domains, however, have not been revealed in the presented topographic experiments because of their small sizes. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The implantations were performed in 4H silicon carbide homoepitaxial layers deposited on (00.1) substrates with 8° offcut, and reference 4H-SiC substrates. The 2 MeV Se+ ions and 1 MeV Al+ ions were implanted with four fluences subsequently increased by the factor of 4-5×. The samples were studied by means of X-ray diffraction topography, high-resolution diffractometry, specular X-ray reflectometry, and Rutherford backscattering spectrometry\channeling method. The dislocation density in the samples evaluated from the diffraction topographs did not exceed 5 × 103 cm−2. The representative roughness values evaluated from the reflectometric measurements was 2.3 ± 0.1 nm for the substrates and less than 1.4 ± 0.1 nm for the epitaxial layers. A significantly higher damage level in the case of 2 MeV Se+ ions in comparison with 1 MeV Al+ ion and a linear increase of the strain with the fluence was indicated, but the highest doses of selenium ions caused the amorphization of the implanted layer. It was also possible to obtain a good fitting of the theoretical and experimental diffraction curves approximating the strain profiles by the distribution of the point defects calculated with the SRIM 2008 code. It was confirmed that the maximum coming from surface damages observed in channeling spectra of the virgin substrate wafers was significantly higher than in the case of epitaxial layers. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The presently studied substrates for manufacturing freestanding silicon epitaxial layers contained two porous layers with different porosities. The upper layers of significantly lower porosity after annealing provided smooth surfaces for deposition of epitaxial layers and the deeper layers of greater porosity enabling easier exfoliation epitaxial foil. The layered structures have been studied by means of synchrotron diffraction topography and by recording of rocking curves from small local area. The most effective method of revealing defects in freestanding exfoliated layers were Bragg-case projection topographs and 'zebra' pattern monochromatic beam topographs providing a map of sample curvature. The samples have been additionally examined by means of high-resolution diffractometry and reflectometry. The porous layers without epitaxial deposition provided strong narrow maximum at low angle side of the substrate maximum common for both of the porous layers. The most probable effect of the deposition of epitaxial layer is the decrease of lattice parameter in the upper layer with lower porosity, which provided the maxima in the diffraction curves located on low angle side of the substrate maximum. The topographic investigations revealed some defects in deposited epitaxial layers, connected with some irregularities of the annealed porous layer. Very characteristic common defects were large caverns, overgrown in the epitaxial process with the diameters of several tenths of micrometers and defects (possibly the overgrown submicron caverns), associated with some bundles of dislocations resolved in the topographs. In layers of large thickness, the characteristic long black and white stripes along <110> have also been observed, which most probably were stacking faults with dislocation loops. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The synchrotron diffraction topography had been widely used for investigation of the structural defects in crystals grown by the Czochralski method. Similarly as conventional diffraction topography, the synchrotron topography consists in recording with high spatial resolution of the beam formed by the Bragg reflection from the crystal. The advantages of synchrotron sources come from the possibilities of using the wavelength from a wide spectral range, improved high spatial resolution and collimation of the beam as well as from shortening the time necessary for the investigation. The synchrotron diffraction topography includes experimentally simpler white beam topography and more complicated monochromatic beam (multicrystal) topography, where the beam is formed by monochromators. In the case of Czochralski-grown crystals the synchrotron diffraction topography can be used for studying of the individual dislocations and their complexes such as glide bands or sub-grain boundaries, individual blocks, twinning, the domain structure and various segregation effects negatively affecting crystal properties. In addition, the topographical investigation can provide information concerning the reasons for the generation of defects, useful in the improving of the technology. In the present paper the possibilities of the synchrotron diffraction topography are discussed on the basis of several investigations of the Czochralski-grown oxide and semiconductor crystals, performed by the authors at HASYLAB. The majority of the results concern the oxide crystals grown at the Institute of Electronic Materials Technology, in particular garnets, orthovanadates, mixed calcium barium and strontium niobates as well as praseodymium lanthanum aluminates. [ABSTRACT FROM AUTHOR]

Undoped 4H silicon carbide epitaxial layers were deposited by means of CVD method with growth rates of 2 μm/h, 5 μm/h and 11 μm/h at 1540 °C on n-doped 8°, 4° and 0° off-cut 4H-SiC (00 · 1) substrates. The structural defects were studied before and after growth of the epitaxial layers by means of conventional Lang topography, synchrotron white beam and monochromatic beam topography and by means of X-ray specular reflectometry. The topographic investigations confirmed the continuation of the dislocations in the epitaxial deposit on the 8° and 4° off-cut substrates without new extended defects. The important difference occurred in the surface roughness of the epitaxial layers, which increased for higher growth rates. The epitaxial layers grown on 0° off-cut substrates at analogous condition contained usually other SiC polytypes, but the influence of the growth rate on the distribution of the polytypes was observed. [ABSTRACT FROM AUTHOR]

A domain structure and crystallographic defects in Czochralski grown single crystals of PrxLa1-xAlO3 and PrxLa1-x-yMgyAlO3 were characterised with a number of methods including conventional and synchrotron X-ray diffraction topography, and polariscopic micrography. The observed twin domain systems were located perpendicularly to {100}pcub and {110}pcub (pseudocubic) directions. It has been confirmed that the domains are of the same orientation and a twin character as those described in literature for LaAlO3 and LaGaO3 crystals. The use of section transmission topography enabled to indicate that the domains are perpendicular to the (100)pcub surface of the samples. The misorientation of lattice in the domains was evaluated from the white beam topographs and a tendency of its increase with increasing concentration of praseodymium was revealed. [ABSTRACT FROM AUTHOR]

The GdVO4 single crystals, both undoped and doped with erbium or thulium, were studied by means of X-ray diffraction topographic methods exploring laboratory and synchrotron radiation sources. Variously developed block structure, caused probably by thermal stresses, was revealed. The highest crystallographic perfection was observed in the crystal doped with 4 at.% of thulium, which was free of the grain boundaries in the end part. Contrary to that, the differences in structural perfection between samples cut out from various regions of the crystal and for different kinds of doping, were less distinct in other crystals. The diffraction topographic methods enabled the statement that the misorientation between various blocks is in the range of several arc minutes. [ABSTRACT FROM AUTHOR]

Defect structure of Czochralski grown silicon (Cz-Si) with nitrogen admixture, cN ⩽ 5×1014 cm-3 (Cz-Si:N), annealed for up to 10 h at 1270-1400 K under hydrostatic Ar pressure ⩽ 1:1 GPa, was investigated by synchrotron diffraction topography (HASYLAB, Germany), X-ray reciprocal space mapping, and infrared spectroscopy. Extended defects were not detected in Cz-Si:N processed at up to 1270 K. Such defects were created, however, in Cz-Si:N pre-annealed at 923 K and next processed at 1270 K or in as-grown Cz-Si:N processed at 1400 K. Investigation of temperature-pressure effects in nitrogen-doped silicon contributes to the understanding of defect formation in Cz-Si:N [ABSTRACT FROM AUTHOR]

Depth distribution of implanted species and microstructure of oxygen-containing Czochralski grown silicon (Cz-Si) implanted with light ions (such as H+) are strongly influenced by hydrostatic pressure applied during the post-implantation treatment. Composition and structure of Si:H prepared by implantation of Cz-Si with H+ 2 ; fluence D = 1:7 × 1017 cm-2, energy E = 50 keV (projected range of H+ 2 , Rp(H) = 275 nm), processed at up to 923 K under Ar pressure up to 1.2 GPa for up to 10 h, were investigated by elastic recoil detection Rutherford backscattering methods and the depths distributions of implanted hydrogen and also carbon, oxygen and silicon in the near surface were determined for all samples. The defect structure of Si:H was also investigated by synchrotron diffraction topography at HASYLAB (Germany). High sensitivity to strain associated with small inclusions and dislocation loops was provided by monochromatic (λ = 0:1115 nm) beam topography. High resolution X-ray diffraction was also used. [ABSTRACT FROM AUTHOR]

The numerical simulation has been applied for studying of Bragg-case section topographic images of dislocation and rod-like inclusions. The validity of simple approximation of extinction contrast was confirmed in the case of screw dislocations in silicon carbide crystals. A procedure for approximate calculation of the strain field of rod-like inclusion was constructed, consisting of adding the contributions from a very large number of point-like inclusions uniformly distributed inside the assumed volume of the inclusion. The procedure ensured a reasonable similarity between the simulated topographs and experimental Bragg-case section topographic images of some pipe-formed cavities in silicon carbide crystals. The method is useful for some other materials, e.g. it enabled to compute realistic simulation of plane-wave topographs of the rod-like inclusions in YAG. [ABSTRACT FROM AUTHOR]

The defect structure of YVO4 single crystals doped with Er3+, Ho3+ and Ca2+ were studied by X-ray diffraction topographic methods, using laboratory and synchrotron radiation sources. Variously developed block structure was the dominating imperfection of the investigated crystals observed both in conventional Lang and synchrotron topographs. The evaluation of block misorientation was realised by means of superimposed projection and section white beam synchrotron radiation topographs. More possibilities of following the mutual rotation of blocks were provided by means of white beam synchrotron radiation WBSR projection topographs exposed through the fine mesh. [ABSTRACT FROM AUTHOR]

X-ray reflectometric and diffraction topographic methods were applied for examination of 4H and 6H silicon carbide substrates finished with various regimes, as well as, silicon carbide epitaxial layers. The investigations indicated a very good quality of the substrate surfaces finished with the process established at the Institute of Electronic Materials Technology, which provided the surface roughness σ = 0:55 ± 0:07 nm for 4H-SiC wafers. These values were better than those of substrate wafers offered by many commercial producers. The surface roughness was decreased during the initial high temperature etching to σ = 0:22 ± 0:07 nm. A relatively good structural quality was confirmed in the case of 4H epitaxial wafers deposited on the substrates prepared from the crystals manufactured at the IEMT, with the 8° off-cut from the main (001) plane. [ABSTRACT FROM AUTHOR]

Effect of stress created by Ar hydrostatic pressure (HP) up to 1.1 GPa during annealing at the high temperature (HT) 1070 K (HT-HP treatment) on microstructure of Czochralski grown silicon co-implanted with helium and hydrogen Si:(He,H) using the same doses of He+ and H2+(DH,He= 5.1016 cm-2, at energy 50 and 150 keV, respectively) was investigated by means of X-ray (synchrotron) diffraction, transmission electron microscopy, and electrical measurements. The nanostructured sponge-like buried layers are formed in Si:(He,H) by annealing / high pressure treatment. Decreased interference, diffuse scattering and individual contrast are observed in the synchrotron topograms for HT-HP treated Si:(He,H). The treatment at 723 K and HP results in an additional donor formation as a sequence of the implantation-disturbed layer. The HP-mediated (retarded) out-diffusion of hydrogen and helium is in part responsible for the effects observed. [ABSTRACT FROM AUTHOR]

Positron angular correlation curves have been measured for nickel in the [100], [110], and [111] directions at room temperature, 330°C and 380°C. Mijnarend's approach is used for their interpretation. For ferromagnetic nickel th 6th zone Fermi Surface (FS) obtained in this way is similar to that obtained from other experimental measurements as well as from band structure calculations. At 380°C the regrouping of the 5th zone electrons at the Curie point is well visible, and information is obtained about the paramagnetic nickel FS in the 6th and 5th zones. Besides, at this temperature the FS in the 6th zone is larger and rounded off. This effect, still needing further experimental confirmation, is attributed to thermal vibrations of the lattice. [ABSTRACT FROM AUTHOR]

Silicon epitaxial layers deposited on substrates doped with boron and containing certain amount of misfit dislocations were studied by means of back-reflection synchrotron section topography. Samples with different curvature determined by substrate thickness and status of their back sides were examined. When the curvature of the sample was negligible the section pattern consisted of two stripes corresponding, respectively, to the layer and to the substrate. Misfit dislocations were revealed in the direct contrast located mostly in the vicinity of the substrate stripe. In the samples with radius of curvature smaller than 100m additional interference fringes were observed in a wide area behind the main two stripes. The sequence of these interference fringes was dependent on the curvature of the sample and differed from that of bent substrate wafers of the similar curvature. As a consequence the images of misfit dislocations became much more extended and contained many characteristic details. The character of experimental misfit dislocation images both in the case of flat and bent crystals was reproduced using numerical integration of the Takagi-Taupin equations. [ABSTRACT FROM AUTHOR]

White-beam synchrotron section topography was applied to a silicon crystal implanted with 4.8 MeV α-particles elastically bent with the radius of curvature close to 100 m. A number of section patterns corresponding to different reflections was analysed. It was found that the section pattern in the bent sample was drastically different from those observed in a flat sample. The difference consists in the occurrence of the sets of additional interference fringes covering a long distance up to several millimetres behind the main diffraction maximum. It was possible to reproduce some characteristic features of the fringes both in the implanted and non-implanted region by numerical integration of the Takagi-Taupin equation. [ABSTRACT FROM AUTHOR]

The samples cut out from Si : Ge crystals with 3% and 1.2% of germanium were studied by means of synchrotron white beam Bragg-case section and projection topography as well as conventional transmission Lang topography. The obtained topographs revealed dominant contrast coming from the segregation of germanium. The use of Bragg-case section topography made possible to follow the shape of growth surfaces inside the crystal. The formation of contrast in Bragg-case section topographs for different orientation of growth surfaces with respect to the incident beam is discussed. The applied methods enabled also revealing growth surface instabilities occurring in some regions of Si : Ge crystals. [ABSTRACT FROM AUTHOR]

The samples cut out from Si : Ge crystals with 3% and 1.2% of germanium were studied by means of synchrotron white beam Bragg-case section and projection topography as well as conventional transmission Lang topography. The obtained topographs revealed dominant contrast coming from the segregation of germanium. The use of Bragg-case section topography made possible to follow the shape of growth surfaces inside the crystal. The formation of contrast in Bragg-case section topographs for different orientation of growth surfaces with respect to the incident beam is discussed. The applied methods enabled also revealing growth surface instabilities occurring in some regions of Si : Ge crystals. [ABSTRACT FROM AUTHOR]